Special mention should be here made of climate, and of its heat or moisture. The lines called isothermal, that is, lines of equal annual heat, are, therefore, of greatest importance to public economy, because the “zones of production” depend mainly on them.(194) However, we are concerned here, not only with the average temperature of the whole year, but especially with the distribution of heat among the several parts of the day and the different seasons of the year, and the maximum summer heat and winter cold (the isothermal and iso-cheimenal lines). Coast lands are wont to have a milder winter and a cooler summer than continental ones with an equal average yearly heat. This produces a great difference in vegetation, because there are a great many plants which can endure the winter’s cold very well, but require a hot summer; and _vice versa_.(195) Were it not for this fact, in connection with the winter-sleep of plants, a large portion of the north would be entirely uninhabitable. Besides, the temperature of a place does not depend exclusively on its latitude, or on its height above the sea-level.(196) The humidity of the climate is, as a rule, great in proportion to the quantity of water in its neighborhood, and to the height of its temperature; although, for instance, in Europe, the number of rainy days increases, the further we advance towards the north.(197) Although the distance of a place from the equator and its height above the level of the sea have, in many respects, a similar effect (vertical, horizontal isothermal lines and zones of production), mountainous regions are uniformly distinguished by a greater degree of humidity, which makes them better adapted for pasturage and forest-culture. But the flora of a locality, being the resultant of all its conditions, affords us a much better criterion of the value of the climate for economic purposes, than the most accurate thermometric observations. Other things being equal, the productive force of nature operates, doubtless, with most energy, in warm climates. The more remote a country is from the equator, the more is its fertility confined to its lowest parts.(198) Greater heat will, as a rule, ripen the same product sooner, and thus permit the same land to be used several times in the same year.(199) Each individual harvest, as a rule, is more abundant,(200) and the products better in many respects. The fruit, for instance, and wine, contain more sugar,(201) and oleaginous plants contain more oil. Lastly, since nature in warm countries is so much more generous, it may be utilized by man with less regard for consequences. There is less need of extensive woods, of large winter supplies, especially for animals;(202) fewer buildings are demanded, and there is also less demand for human and brute labor, since the work of plowing, sowing etc., extends over a greater portion of the year.(203) It is true, on the other hand, that also